This patent application is in a similar field to the applicant's earlier PCT application WO2008/139216, the contents of which are incorporated herein by reference. WO2008/139216 describes a way to inductively measure the angle of a contactless target. The system is relatively immune to lateral misalignments of the target relative to the sensor, while at the same time providing relatively large signal levels due to the use of a resonator with a high O-factor. However the embodiments shown in WO2008/139216 used a target placed across the axis of the sensor. This is acceptable for measuring the angle of a rotating shaft when the target can be placed at the end of the shaft (“end shaft operation”). However if the shaft must pass through the sensor and target (“through shaft”) the system described in WO'216 is not appropriate.
This patent application describes a number of improvements to the earlier design described in the above PCT application that allow for through shaft operation while retaining the benefits of immunity to lateral misalignment and high signal levels.